Electric heater with forced air module

ABSTRACT

An electric heating unit ( 10 ) is provided. The electric heating unit ( 10 ) includes a housing ( 12 ) with a chamber and an electric heating element ( 14 ) located within the chamber and extending substantially a length of the chamber. A forced air module ( 16 ) is included having a blower ( 32 ) in flow communication with a first end ( 38 ) of an air plenum ( 34 ). The air plenum ( 34 ) is located adjacent the heating element ( 14 ) and extends a length of the heating element ( 14 ). The air plenum ( 32 ) is configured to discharge air across the heating element ( 14 ) uniformly along the length of the heating element ( 14 ).

TECHNICAL FIELD

This invention relates to heater units. More specifically, it relates to electric heater units with forced air modules for forcing air across its heating element.

BACKGROUND OF THE INVENTION

Portable electric heaters are well known in the art. One particular type is known as a baseboard heater. As implied by “baseboard,” this type of heater is typically low to the ground and of an elongated length. These heaters typically include a housing, an electric heating element located within the housing and an electronic control system to control the cyclical energization of the heating element. The control system typically would include a thermostat for detecting the ambient air temperature. In response the control system would periodically energize the heating element to maintain the room temperature within a certain pre-set temperature range.

Typical baseboard heaters of this type rely primarily on convection to distribute the heat to the surrounding room. That is, as the heating element would energize, its temperature would begin to rise and the temperature of the air immediately surrounding the heating element would also begin to rise. As this air begins heat up, it rises and moves away from the heating element and out of the housing through discharge vents. This air is replaced by air from below the heating element that has moved into the housing through inlets usually located at or near the bottom of the housing. In this way a circulation pattern is established that delivers heated air to the room and supplies cool air to the heater to be warmed by the heating element.

This arrangement has disadvantages. Depending on the above described phenomenon to move air across the heating element results in a flow of air across the element that is uneven along the length of the heating element. That is, the flow of air across the element in one spot, may be greater than that at another location of the element. This results in inefficient operation of the heater. It also results in there being hot and cold spots along the length of the heating element, shortening the length of the life of the heating element.

Additionally, this arrangement results in the housing becoming very hot. It also results in slow heating of the surrounding environment. This is because the rate of flow of air developed through this natural convection process is typically quite low.

Other designs of baseboard heaters use an open blade fan inside the heater housing to stir the air inside the housing. This causes heated air to re-circulate within the housing, causing the housing to also become very hot. This design typically requires the use of baffles and/or reflectors within the housing to help reduce the exterior temperature of the housing

Another known design utilizes a fan that feeds air into an air plenum located below the heating element. The plenum has a uniform cross section along its length and has evenly distributed air vents located along its upper surface. The air forced into the plenum discharges through the vents and across the heating element, becoming heated. The heated air exits the heater through vents located near the top of the housing. The exterior temperature of the housing is improved somewhat by this design as compared to the above-described designs. However, this prior design still results in hot and cold spots along the length of the heating element. The air pressure within the plenum drops substantially linearly along its length from the end where the fan might be located to the other end. This pressure drop results in an uneven flow of air discharging from the plenum. Accordingly, the air flow across the heating element is uneven and results in cold and hot spots along its length.

The present invention is provided to solve these and other problems.

SUMMARY OF THE INVENTION

An electric heating unit is provided. The electric heating unit includes a housing having a chamber and an electric heating element located within the chamber and extending substantially a length of the chamber. A forced air module is included having a blower in flow communication with a first end of an air plenum. The air plenum is located adjacent the heating element and extends a length of the heating element. The air plenum is configured to discharge air across the heating element uniformly along the length of the heating element.

In another aspect of the invention, the blower comprises a radial fan blower and a duct to direct air discharged from the radial fan blower into the air plenum.

In another aspect of the invention a cross sectional area of the air plenum varies along the length of the air plenum.

In another aspect of the invention, a cross sectional area of the air plenum decreases along its length from the first end of the plenum towards a second end of the plenum.

In another aspect of the invention, the air plenum comprises an elongated slot facing the heating element.

In another aspect of the invention, the elongated slot has a variable width along its length.

In another aspect of the invention, the width of the elongated slot increases along its length from an end of the slot proximal the first end of the plenum towards a second end of the slot.

In another aspect of the invention, the air plenum comprises a plurality of apertures facing the heating element.

In another aspect of the invention, the plurality of apertures are generally evenly distributed along the length of the air plenum.

In another aspect of the invention, each aperture is equally sized.

In another aspect of the invention, the apertures increase in size along the length of the air plenum from the first end of the air plenum towards a second end of the air plenum.

Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electric baseboard heater according to the invention;

FIG. 2 is a front view of the heater of FIG. 1 with a portion of the front of the housing cut away to reveal various internal components;

FIG. 3 is a top view of the heater of FIG. 1; and

FIG. 4 is a cross sectional side view of the heater of FIG. 1.

DETAIL DESCRIPTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.

An electric heating unit 10 is shown in the Figures. The heating unit 10 includes a housing 12, a heating element 14, a forced air module 16 and a control system. The housing 12 includes a main body 20 and end caps 22, 24. The main body 20 includes a lower inlet 26 and an upper discharge 28. The housing 12 also includes a pair of support structures or legs 30 adapted to hold the main body 20 of the housing 12 a distance above the floor or other generally flat surface on which the unit 10 may be placed.

The heating element 14 is located within the housing 12, generally in its upper half. The heating element 14 depicted in the figures is a stitch wire, 900/1500 watt, resistive heating element and is commonly known in the art. The heating element 14 includes a plurality of fin- like loops or extensions 15. An alternative heating element 14 that may be used with this heater is a medium-filled passive heating element as disclosed in U.S. Pat. No. 6,072,938, which is incorporated herein by reference. Any of a number of known heating elements may equally be used with the present invention, so long as it is adapted to heat air as it passes by the heating element.

The forced air module 16 includes a radial fan blower 32 ducted to an elongated air plenum 34. The air plenum 34 is located below the heating element 14 and extends substantially the length of the heating element 14. In the embodiment shown, the air plenum 34 extends past an end 36 of the heating element 14. The blower 32 is located near an open end 38 of the air plenum 34 and is adapted to blow or force air into the air plenum 34. A closed end 40 of the air plenum 34 is distal from its open end 38. An upper surface 42 of the plenum 34 includes air exit means 44. The air exit means 44 depicted in the figures is a series of apertures 46. The apertures 46 are all of the same size. That is, the area of each aperture 46 is identical to that of each of the other apertures 46. Also, the apertures 46 are equally distributed about both the length and width of the upper surface 42 of the plenum 44.

It can be seen that the cross section of the air plenum 34 tapers from a larger cross section near the open end 38 to a smaller cross section near its closed end 40, to be explained further.

The control system is typical of those known in the art. It may include a master power switch 48 and a thermostatic control switch or thermostat 50. Not shown, but also included is a traditional power cord for connecting the control system 18 and other internal components of the heating unit 10 with a source of electrical power, typically a standard residential electrical outlet.

In operation the user will connect the power cord to an electrical outlet or other source of electrical power. Moving the power switch 48 to an on or energized position will electrically connect the control system 18 and internal components of the heater 10 to the source of electrical power. The user can then adjust the thermostat 50 to the desired temperature or temperature range. If the thermostat 50 detects that the ambient temperature is at or above the desired temperature range, the thermostat 50 effectively operates as an open electrical switch, electrically disconnecting the heater from the electrical power source. If the thermostat 50 detects that the ambient temperature is below the desired temperature range, the thermostat 50 operates to connect the heating unit 10 to the source of electrical power. In this instance, electric power is supplied to both the heating element 14 and the forced air module 16. Accordingly, the temperature of the heating element 14 and its loops 15 begins to rise. Also, the radial fan blower 32 begins to rotate. This draws cool room air into the housing 12 through the lower inlets 26 and axially into the radial blower 32. Additional venting, perhaps in the form of a grill, may be incorporated into the face of the housing to feed the blower 32 with air. The blower 32 discharges this air into the air plenum 34, pressurizing same. As the fan 32 pressurizes the plenum 34, it forces the air out of the plenum 34 through the apertures 46. This air is directed to flow past the heating element 14.

As seen in FIG. 4, the air discharged from the plenum 34 moves in a vertical direction. The upward movement of the air out of the plenum 34 draws additional cool air from the surrounding atmosphere into the inlet 26, past and around the plenum 34 and past the heating element 14. After the now-heated air passes the heating element 14, it continues in a generally vertical direction and exits the housing 12 through the upper discharge 28 and disperses throughout the surrounding environment.

The forced air module 16 is configured to maintain a uniform flow of air across the heating element 14. The module 16 is also configured to maintain a relatively uniform pressure within the plenum 34 along the length of the plenum. This is accomplished through the combination of the variable cross section of the air plenum 34 with the even distribution of apertures 46 of equal size on and through the upper surface 42 of the plenum 34. This combination results in a relatively uniform air pressure within and throughout the air plenum 34 and a relatively even flow of air across the heating element 14 along the length of the heating element. That is, the flow of air across the heating element 14 at any point along its length is relatively equal to the flow of air across the heating element 14 at any other point along its length. This results in substantially eliminating any hot and clod spots along the length of the heating elements.

It is noted that changes may be made to the configuration of the shape and size of the plenum 34 and/or the air exit means 44 and still remain within the scope of this invention by achieving a substantially uniform flow of air across the heating element 14 along its length. For instance, rather than the apertures 46 described above, a single narrow slot or slit of uniform width may be incorporated into the plenum 34. Multiple slits may be incorporated into the plenum 34 in place of the apertures 46, provided they are evenly distributed about the upper surface 42. For example, a pair of parallel slots may be utilized.

Also, it is possible to utilize a plenum 34 having a constant cross section along its length. In this case, the air exit means 44 may be adjusted or modified to result in a relatively even flow of air across the heating element 14 along its length. For example, a single slot of varying width may be utilized in place of the above-described apertures 46. The width of the slot could increase generally linearly along its length from an end proximal the open end 38 to an end of the slot proximal the closed end 40 of the plenum 34. Apertures 46 of varying size could also be used in the situation of a constant cross section air plenum 34. These apertures could be arranged with smaller apertures located near the open end 38 and larger apertures located near the closed end 40 of the plenum 34.

While the specific embodiments and various details thereof have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the following claims. 

1. An electric heating unit comprising: a housing with a chamber; an electric heating element located within the chamber and extending substantially a length of the chamber; a forced air module spaced from the electric heating element and having a blower in flow communication with a first end of an air plenum, the plenum located adjacent the heating element and extending a length of the heating element; wherein the air plenum is configured to discharge air across the heating element uniformly along the length of the heating element.
 2. The electric heating unit of claim 1 wherein the blower comprises a radial fan blower and a duct to direct air discharged from the radial fan blower into the air plenum.
 3. The electric heating unit of claim 1 wherein a cross sectional area of the air plenum varies along the length of the air plenum.
 4. The electric heating unit of claim 1 wherein a cross sectional area of the air plenum decreases along its length from the first end of the plenum towards a second end of the plenum.
 5. (canceled)
 6. (canceled)
 7. (canceled)
 8. The electric heating unit of claim 1 wherein the air plenum comprises a plurality of apertures facing the heating element.
 9. The electric heating unit of claim 8 wherein the plurality of apertures are generally evenly distributed along the length of the air plenum.
 10. The electric heating unit of claim 9 wherein each aperture is equally sized.
 11. (canceled)
 12. An electric heating unit comprising: a housing with a chamber; an electric heating element located within the chamber and extending substantially a length of the chamber; a forced air module spaced from the electric heating element and having a blower in flow communication with a first end of an air plenum located adjacent the heating element and extending a length of the heating element, the blower for pressurizing the air plenum; wherein the air plenum is configured to maintain a generally uniform air pressure within the plenum and along its length.
 13. The heating unit of claim 12 wherein the air plenum is configured to discharge a uniform mass flow of air across the heating element along the length of the heating element.
 14. The electric heating unit of claim 13 wherein the air plenum includes a series of apertures of uniform size facing the heating element.
 15. The electric heating unit of claim 13 wherein the air plenum includes a series of apertures facing the heating element, the apertures being evenly distributed along a length of the plenum and of varying sizes wherein the size of each aperture increases along the length of the plenum from the first end of the of the plenum towards a second end of the plenum.
 16. (canceled)
 17. (canceled)
 18. (canceled)
 19. The electric heating unit of claim 12 wherein a cross sectional area of the air plenum varies along the length of the air plenum.
 20. The electric heating unit of claim 12 wherein a cross sectional area of the air plenum decreases along its length from the first end of the plenum towards a second end of the plenum.
 21. An electric heating unit comprising: an electric heating element; and a forced air module spaced from the electric heating element and for directing a flow of air across the heating element and comprising an air plenum; wherein the air plenum is configured to maintain a generally uniform air pressure within the plenum.
 22. The electric heating unit of claim 21 wherein a cross sectional area of the air plenum varies along the length of the air plenum.
 23. The electric heating unit of claim 1 wherein a cross sectional area of the air plenum decreases along its length from the first end of the plenum towards a second end of the plenum. 